Means for producing synchronous motion.



PATENTED .APR. 28

L. M. POTTS. MEANS FOR PRODUCING SYNOHRONOUS MOTION.

APPLICATION FILED DEG. 10, 1901.

2' SJIBETS-SHE'ET 1.

NO MODEL.

lwueufoz 1 2301 I name:

JWM

No. 726,750. I PATENTED APR. 28, 1903.

L. M. POTTS. 4 MEANS FOR PRODUCING SYNGHRONOUS MOTION.

APPLICATION FILED DBO. 10, 1901.

N0 MODEL. 2 SEEETSSHEET 2.

' I: ai j I I I THE NORR S TLRS CD P G A U ITED STATES PATENT OFFICE.

LOUIS MAXWELL POTTS, or BALTIMORE, MARYLAND, ASSIGNOR TO ROWLAND TELEGRAPHIC COMPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF NEW JERSEY.

MEANS FOR PRODUCING SYNCHRONOUS MOTION.

SPECIFICATION forming partof Letters Patent No. 726,750, dated April 28, 1903. Application filed December 10, 1901. Serial No. 85.349. (N0 model.)

To all whom it may concern:

Be it known that I, LOUIS MAXWELL Poms, a citizen of the United States, residing at Baltimore, in the State of Maryland, have invented certain new and useful Improvements in Means for Producing Synchronous Motion, (Case 0;) and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appert-ains to make and use the same.

This invention relates to improvements in the production and maintenance of synchronous motion between two or more rotating or vibrating bodies near together or separated by long distances and may be employed to maintain two or more bodies in motion having any definite speed relation. the one to the other.

The invention more especially relates to improved means for running electric motors in synchronism with or at any speed bearing a definite relation to that of another rotating or vibrating body.

To this end the said invention consists in maintaining synchronism by closing and opening at definite intervals a shunt-circuit of resistance, capacity, or self-induction around the motor-armature or the fields, or both the armature and fields, or around a resistance is series with either or both.

The invention is applicable to any size of motor-series, shunt, or compound Woundand of any construction, with the limitation that the full voltage of the power-circuit must not be acting on either the armature or the fields.

According to the present invention no extra load is thrown on the motor, nor does the regulation depend upon the reversal of the field or armature current. Hence the spark: ing which necessarily results in the latter case is reduced to a minimum or practically zero.

The present invention, moreover, contemplates the maintenance of synchronous motion between two movinghodies in such manner thatthe regulating effect is produced for only one or for any definite number of relative positions of the two bodies.

In order to more fully describe the said invention, reference will be had to the accompanying drawings, in which- Figures 1, 2, and 3'are diagrams illustrating the principle of my invention and showing in three operative positions the arrangement of the apparatus for short-circuiting the motor-armature. Fig. 3 is a diagram illustrating the case in which the motor is driven in synchronism with a distant bodyand in which a relay is employed instead of a rotary circuit-changer. Fig. 4 is a diagram illustrating the principle of regulation by short-circuiting the motor-fields, and Fig. 5 is a diagram illustrating the principle of regulation by shortcircuiting both armature and fields. Fig. 6 is a diagram illustrating the case in which the invention is used to maintain synchronism for only one or any definite number of relative positions of two bodies; and Fig. 7 is a diagram illustrating the case in which synchronism may be maintained between two distant motors or other bodies in communication over a single wire by the use of this wire for a small port-ion of the total time, the wire being used for the remainder of the time for any other purpose.

Similar letters and numerals refer to similar parts throughout the several views.

Referring first to Figs. 1 to 3, or represents the motor to be synchronized, 1 the development of a rotary circuit-changer mounted upon the armature-shaft of said motor or otherwise mechanically or electrically driven in synchronism therewith, and 2 the development of a rotary circuit-changer operating in synchronism with the body with which synchronism is to be established. 'lhese circuitchangers are in the special case shown composed each of two metallic sections having interlocking segments and brushes 5 c d and of g, respectively, which are disposed upon the face of said circuit-changers, as shown, so that as the circuit-changers rotate electrical connection will be made between the respective central brushes and first one and then'the other of their side brushes alternately.

The term circuit-changer is applied to the devices l and 2 for the lack of a better term, it being understood that they do not l illl llllllllll r r liilli llllllfil l lllllllt perform the function of pole-changers in the sense of reversing the polarity of the current, but simply act to change the circuit alternately from first one pair of brushes to another. Moreover, it is obvious that either the brushes or cylindrical portions of the circuit-changers may be rotatable without alter ing the principle thereof; but it will be assumed that the brushes are stationary and the cylindrical portion rotates and does so in the direction of the arrows. Furthermore, these circuit-changers may be provided with any desired numberot' segments, and, as will be hereinafter shown, may be replaced by relays or by any suitable devices whereby circuits may be periodically made and broken.

The central brushfis connected, as shown, through a suitable resistance r with the positive brush h of the motor, While the central brush 0 is connected to the negative brush of said motor. The resistance r is necessary for preventing the short-circuiting of the motorarmature, as practically all of the potential drop in the motor is in the armature, the one hundred and ten volts or other supplying-circuit would be sent through the fields which would damage the motor and produce such sparking at the brushes as would destroy the commutator and brushes in a very short time. This would, moreover, result in regulation too violent for practical purposes. By giving a proper value to the resistance 7", however, all of these objections may be overcome and the synchronism still remain strong, the strength of the synchronism depending upon the value of the said resistance.

The respective right-hand brushes d g and left-hand brushes Z) c are connected together as shown. By this arrangement the circuitchangers are connected in shunt around the motor-armature.

With the above arrangement the operation of establishing synchronism consists in varying the speed of the motor a to correspond with any variation in the speed of the circuitchanger 2 or other device with which synchronism is to be established by varying the time that a shuntcircuit is completed around the armature. The regulating apparatus must, therefore, be capable of com pleting this shunt-circuit for an indefinite number of intervals each corresponding to a definite speed of the apparatus with which synchronism is to be established. It for a state of synchronism the speed of the motor should be high, the time intervals for which the shunt-circuit is on should be correspondingly short, and if the state of synchronism requires a slow speed of the motor the time intervals for which the shunt-circuit is on should be correspondingly long, and so on with the indefinite number of different speeds required, it being understood that a short circuit or shunt completed around the motor-armature diminishes or tends to diminishitsspeed. Therefore,dependingupon the relative positions of the brushes of the respective circuit-changers, we have for a state of synchronism either the short circuit around the armature-circuit continuously, continuously broken, or between these two extreme relations of the brushes,an infinite number of relations for each of which the shunt is around the armature a different proportion of the total time, and consequently the motor will run at different speeds for a different phase relation of the said brushes. It must be understood, however, that this regulating effect is not in the nature of a correct-rix that is to say, the synchronizing force does not wait until synchronism is disturbed and then cause the motor to slow down or speed up, as the case may be, and fall again into synchronism, but the synchronizing force acts continuously, so that if the device with which synchronism is being maintained varies its speed in the slightest degree the motor follows every variation.

In starting up, the motor is brought up to approximately the correct speed by any ordinary method of adjustment, as by a rheostat, and in the case 'of shunting the armature is set so as to have a normal tendency to run too fast.

Referring to Fig. 1, let it be assumed that circuit-changers 1 and 2 are rotating in synchronism and have attained a constant state with the phase relation of the brushes, as indicated. When the brushes occupy this relation, taking the full-line position of the brushes, the shunt-circuit h fg d c 2' will be completed around the motor-armature. The fields will therefore become strengthened and thearmature-currentdiminished. Next,suppose the circuit-changers are still in synchronism, but have advanced so as to bring the brushes to the dotted-line position or from position 00 to position 1 the short circuit is still maintained, but will take the course h f e" b c 2'. Likewise the shunt-circuit will be maintained continuously as long as the brushes maintain the phase relation indicated, or, more generally, as long as c and f arrive simultaneously upon corresponding points of their right-hand and left-hand sections of the circuit changers, respectively. This is one extreme phase relation or relation of minimum speed and maximum length of time of short-circuiting. This condition is, however, maintained indefinitely as long as synchronism is maintained and the phase relation of the brushes remains unaltered. Next, suppose the circuit-changers are rotating in synchronism, but that the phase relation between the brushes has been changed-as, for example, by the lagging of the circuit-changer 2 until its brushes have advanced relatively the distance of one segment that is, the phase difference has changed one hundred and eighty degrees. (See Fig. 2.) Starting from h, as before, it will be seen that the circuit can be traced from h tc-f to e to b; but from b to c the circuit is broken. Hence the shunt-circuit will not be completed around the armature, and

this circuit will remain broken from b to c as the brushes pass from the full-line position to the dotted position, when the circuit will still remain open, but in this case will be broken between d and 0. With this phase relation it will therefore be seen that the short circuit around the armature is continuously broken and, indeed, will remain so as long as the brush 0 arrives upon a given point of a segment of its righthand section at the same time that the brush f arrives upon a corresponding point of a segment of its left-hand section, and vice versa, the respective segments not necessarily corresponding. This is the phase relation of shortest length of time of shunting the armature, or,more correctly, the relation of the shunt-circuit continuously broken, and hence the relation of maximum speed of the motor. Therefore, depending on the relative position of the brushes, we may have for a state of synchronism the shunt-circuit around the armature-circuit continuously or continuously broken and between these two extreme relations of the brushes an infinite number of relations, for each of which the shunt is around the armature a diiferent proportion of the total time, and consequently the motor will run at different speeds for different phase relations of the said brushes.

In the case of any of the phase relations between the two extremes the shunt-circuit is on and off at rapidly-recurring intervals, so that the governing effect is the integral result of the series of shunt-circuits. In other words, the action between the two extreme conditions above pointed out isintermittent, and the speed varies as the length of the periods that the shuntcircuit is on or off. In Fig. 3 is shown one of these intermediate phase relations. Here it will be seen that as the brushes pass from the position a: to the position y the shunt-circuit is broken from b to 0; but as they pass from position 'y to position z the shunt-circuit is closed, so that half the time the shunt is broken and half the time it is completed, assuming that the devices are maintaining a state of synchronism. But suppose that due to some disturbance pole-changer 2 speeds up. This may be considered equivalent to pole-changer 2 moving upward in the direction of the arrows on r the drawing and the brushes remaining sta tionary. Then suppose,for example,thatpolechanger 2 speeds up for such a length of time that it is advanced the distance of half a segment, or a distance equal to the distance from as to 3 on pole-changer 2. The relative positions of the pole-changer and brushes will then be such as to produce the same effect as the arrangement shown in Fig. 2-that is, the brushes efg, Fig. 3, will be one segment behind the brushes 1) 0 cl, when the short circuit will be opened a greater length of time.

The motor and pole-changer 1 will therefore increase their speed and maintain synchronism. Ihis speed is then preserved until another disturbance necessitates a change of phase to maintain synchronism.

A better idea of the practical arrangement of the system may be had from Fig. 3?, in which I have shown a case for producing synchronism between the motor a and a distant body-such as a dynamo, motor, or other body. In such a case as this if the rotary circuit-changer, such as 2, were employed it would be necessary to use a small synchronous motor or the like to drive the said circuitchanger in synchronism with the dynamo or motor at the distant point. It is preferable, however, to employ in such a case instead of the rotary circuit-changer 2 a relay 2, which is the exact electrical equivalent of the said circuit-changer, and operate this relay by means of a periodically-varying current in the line L, which connects the said relay with the body with which synchronism is to be maintained. In the drawing I have represented this body as being an alternating-current dynamo j; but it may be any moving device for sending a periodically-varying or other governing current over the line L. In this case the motor ais connected to the circuit-changer 1 in exactly the same manner as described with reference to Figs. 1, 2, and 3. The contacts 6 and g are connected to the brushes 1) d and the tongue f of the relay is connected to the resistance r. The tongue of the relay 2-will therefore vibrate in unison with the currentin the line L and with the dynamoj or other device, which sends the periodically-varying current to the said line, and the coaction between the relay 2' and the circuit-changer l is exactly the same as between the circuit-changers 1 and 2 described with reference to the foregoing figures. The period of vibration of the relay-tongue corresponds exactly to the passage of the circuit-changer brushes over the sections of the cylinder. Therefore if the dynamo or motor j changes its speed the period of vibration of the relay-tonguef will also change, and as this changes the phase relation between the said tongue and the circuit-changer 1 this will either increase or diminish the length of the intervals for which the shuntcircuit is completed around the motor-armature, and therefore will cause the motor Ct to follow every vibration in speed of the dynamo or other distant body, as described.

Inasmuch as the relay and rotary circuit changer are exact electrical equivalents, the term "circuit-changer is employed in the claims'to cover both devices or any equivalent thereof.

It will be seen that the arrangement shown in Fig. 3" is adapted to short-circuit the motor-armature; but obviously these connections maybe used also to short-circuit. the fields, as hereinafter described, or both fields and. armature.

A case in which the regulation is effected by shunting the motor-fields instead of the armature is shown in Fig. t. The arrangement of the circuit-changers 1 and 2 is the same in this case as in those above described, and the operation is the same with the exception' that in this latter case as the shuntcircuit is around the fields the speed of the motor is increased by the shunt-circuit in stead of being diminished thereby, as described in the foregoing case. Moreover, the regulation may be efiected by shunting both armature and fields. Such a case is shown in Fig. 5. In this event an extra brush is is added to the circuit-changer 1 and connected to the positive field terminal, preferably through a resistance r, the rest of the connections remaining the same as in Fig. 1. The brush has a lead of one segment with respect to the brush 0, or, more generally stated, the brushes 0 and 7c occupy at all times corresponding positions on segments of opposite sections. Therefore the brush lo may havea lead of one or any number of segments so long as they preserve the relation stated above. In this case the shunt-circuit is continuously around the armature or continuously around the fields or intermittently on first the fields and then the armature for various proportions of the time dependent upon the phase relation of the brushes of the respective circuit-changers.

From the foregoing description it will be seen that synchronism may be established for any given phase relation between the circuit-changers.

A special case in which synchronism may be maintained for only one of a definite number of phase relations is shown in Fig. 6, in which 4: and 5 represent the developments of two cylinders provided with the solid ring portions 4 5 and the segments 4 5, respectively, and connected, as shown, the said cylinders corresponding to the above-mentioned circuit-changers, and m n and 0 p short-circuited brushes which rest upon the said cylinders, as shown. If one segment of one cylinder is connected to a directly-opposite segment of the other cylinder, as shown, the shunt will be connected around the motor only when the brushes pass over the two segments simultaneously or, in other words, occupy the phase relation shown. If they do occupy this phase relation, the shunt will be completed once in each revolution; but if the brushes do not maintain this relation then the shunt will not be established. The length of time that any shunt is completed depends (considering the breadth of the segment a constant quantity) upon the angular position of the brushes n and 0. If they both occupy the same angular position, then the shunt will be completed for the entire time that they are passing over a segment; but this time will be diminished as the angular displacement between the two brushes increases until they are displaced the distance of a segment, when the shunt-circuit will not be completed at all.

If segments diametrically opposite from those shown connected in Fig. 6 are similarly "mane connected, there will be two positions of synchronism one hundred and eighty degrees -apart, and by similarly connecting corresponding segments all around there may be as many positions of synchronism as there are segments 4. or 5. Obviously this arrangement may be used also for shunting the motor-fields.

Instead of making use of the whole of the periphery of the circuit-changer cylinders, as shown in Figs. 1 to 6, I may employ only a portion of the periphery for synchronous purposes by constructing the circuit-changer cylinder l as shown in Fig. 7, the brushes remaining the same. The operation of maintaining synchronism in this case is just as described relative to the foregoing figures. I have also shown in Fig. '7 a relay 3 substituted for the circuit-changer 2. The relay 3 is operated by periodically-varying current in the line L from any desired source, and its operation is just the same as that of the circuitchanger 2, the two being exact electrical equivalents. In the case of the relay the shunt-circuit depends upon the period of vibration of the relay-tongue instead of the angular position of the brushes of the-circuitchanger 2. In fact, the case shown in Fig. 7 is exactly the same as that shown in Fig. 3, except that in Fig. 7 only a portion of the circuit-changer is used for synchronizing.

Although in the drawings I have shown a series-wound motor I do not wish to be understood by this as confining the invention to such a specific application, as the principle is applicable to the synchronism of shunt and compound wound motors as well as to series motors.

Having thus described my invention, it is obvious that there are many changes and modifications which may be made therein withoutdeparting from the spirit thereof; but

What I claim, and desire to secure by Letters Patent of the United States, is-

, 1. The combination with an electric motor, *of a body with which said motor is to be synchronized, a shunt-circuit, and means for exerting a continuous synchronizing effect upon said motor by intermittently closing said IIO shunt-circuit'around the armature of said motor.

2. The combination of an electric motor, of a body with which said motor is to be synchronized, and means for synchronizing said motor by intermittently shunting the armature and field-current of said motor.

3. The combination with an electric motor, of a body with which said motor is to be synchronized, and means for synchronizingrsaid motor by intermittently shunting the fieldcurrent of said motor;

4. The combination with an electric motor, of a body with which said motor is to be synchronized, a shunt-circuit containing one or more electrical constants, and means for synchronizing said motor by alternately shunting the armature and field currents thereof through said circuit at definite intervals, the length of said intervals varying as the said motor changes its phase relative to the body with which synchronism is to be maintained.

5. The combination with an electric motor, of a body with which said motor is to be synchronized, a shunt-circuit containing one or more electrical constants, and means for synchronizing said motor by shunting the armature-current thereof through said circuit at definite intervals, the length of said intervals varying as the said motor changes its phase relative to the body with which synchronism is to be maintained.

6. In a synchronizing system, the following instrumentalities, viz: an electric motor and a body with which said motor is to be synchronized, a circuit-changer operating in synchronism with said motor and a circuitchanger operating in synchronism with said body, a shunt-circuit completed at definite intervals through both circuit-changers, the length of time for which said shunt is completed at each interval, varying as the said motor varies its phase relative to said body with which synchronisin is being maintained.

7 In a synchronizing system, the following instrumentalities, viz: an electric motor and a body with which said motor is to be synchroniz'ed, a circuit-changer operatingin synchronism with the said motor and a circuit-changer operating in synchronism with said body, and a shunt-circuit, said circuit changers cooperating to complete said shuntcircuit around the armature and field of said motor at definite intervals, the length of which varies as the phase relation to the said motor and said body is varied.

8. In a synchronizing system, the following instrumentalities, viz: an electric motor and a body with which said motor is to be synchronized, a circuit-changer governed by the speed of the said motor and a circuit-changer governed by the said body, and a shunt-circuit containing one or more electrical constants, said circuit-changers coacting to complete said shunt-circuit around the armature of said motor at definite intervals, the length of which varies as the phase relation between said circuit-changers varies.

9. In a synchronizing system, the following instrumentalities, viz: an electric motor and a body with which said motor is to be synchronized, a circuit-changer governed by the speed of said motor and a pole-changer operating in synchronism with the said body, a governing-circuit controlling the motion of the second circuit-changer, and a shunt-circuit containing one or more electrical constants, said circuit-changers coacting to complete said shunt-circuit around the armature of said motor at definite intervals which vary in length as the phase relation between said circuit-changers varies.

10. In a synchronizing system, the combination with an electric circuit, and a controlling-current traversing said circuit, of a body controlling the current-flow in said circuit and with which synchronism is to be maintained, a circuit-changer controlled by the current in said circuit, a motor to be synchronized, a circuit-changer controlled by said motor, a local governing-circuit including both of said circuit-changers, the said circuitchangers acting to shunt the motor-driving current through the said circuit continuously, to keep said circuit continuously broken, or closed and broken at intervals as the state of synchronism may require, the said intervals varying in duration as the said motor varies its phase relative to said body.

11. In a synchronizing system, the combination with an electric motor to be synchronized, of a body with which synchronism is to be maintained, a rotary circuit-changer driven by said motor, a circuit-changer governed by said body, a shunt-circuit including both of said circuit-changers and connected around the armature of said motor, said circuit being adapted to be completed and broken by the cooperation of said circuitchangers and thereby to exercise a synchronizing effect on said motor independent of an electromotive force in said shunt other than that acting to drive the said motor.

In testimony whereof I affix my signature in presence of two witnesses.

LOUIS MAXWELL PO TTS.

Witnesses PAUL MASSON, FREDK. STEVENSON. 

